Many machines, such as fans and engines, produce noise during operation. Perforated enclosures used to protect the machine and facilitate air flow to and from the machine can increase the noise. For instance, in order to protect an engine from damaging elements, such as debris and sand, the engine generally is surrounded by an engine housing. The engine housing includes perforations, herein referred to as air flow openings, that allow air flow to and from the engine. Often, the air flow openings are included within at least one detachable sheet metal panel attached to the engine housing. Although the air flow openings are necessary to the operation of the engine, the openings within the panel have become outlets for engine noise.
Over the years, various methods of reducing engine noise through the air flow openings of engine housings have been developed. For instance, a silencer with multiple acoustic louvers may be positioned between the engine and the housing panel. Some of the sound created by the engine and exiting through the air flow openings of the panel will be absorbed by the acoustic louvers. Although the acoustic louvers help attenuate engine noise, the approach is relatively costly being that the silencer includes multiple parts, including frames, retaining screens and louver panes. Moreover, a separate grille, needed to protect the louvers from damaging elements, often overlaps with the louvers, restricting air flow to and from the engine. In addition, the acoustic louver silencer generally cannot fit within small and/or irregular shaped spaces, and thus, may not be suitable for some engines.
Another approach is to position a baffle made, in part, from acoustic media between the engine and the housing panel. Although the acoustic baffle can absorb some of the sound created by the engine, air flowing to and from the engine must flow around the baffle. Although the acoustic baffle may attenuate engine noise, the acoustic baffle unduly restricts the air flow.
The present disclosure is directed at overcoming one or more of the problems set forth above.